1. Field
The present disclosure relates generally to composite structures and, in particular, to inspecting composite structures. Still more particularly, the present disclosure relates to a method and apparatus for quantifying and characterizing resin on a composite structure.
2. Background
Composite structures are generally comprised of layers of resin-infused fiber. The layers of fiber may take the form of cloth, tape, or other suitable forms. The resin may already be infused in these layers or added while the layers are laid up to form the composite structure.
In fabricating composite structures with these types of layers, an inconsistency in the manner in which a layer is laid up with respect to other layers may result in an undesirable feature in the composite structure. For example, a wrinkle in one layer of fiber may propagate to other layers all the way to the surface of the composite structure. This propagation may form a depression in the surface of the structure. Resin may fill this depression during curing of the layers. This situation may result in a region in which the resin is thicker than in other areas. This type of region may be referred to as a pocket or a resin pocket.
Inspection of composite structures may be performed using non-destructive techniques (NDT). These techniques may include the use of ultrasonic systems. These types of systems, however, may not provide an ability to detect regions of resin containing an undesired thickness. For example, ultrasonic systems may be useful in detecting regions of resin that are over about 40 mils. However, for regions less than about 40 mils, the accuracy of the measurements may be lower than desired and make the measurements unreliable.
Therefore, it would be desirable to have a method and apparatus that takes into account the issues discussed above as well as possibly other issues.